In order to allocate downlink or uplink resources to M2M devices, a base station has to know that a corresponding device has what type. In an M2M system, a lot of (about several hundreds of times to several thousands of times) devices may exist in a cell as compared with the existing system (802.16e or 802.16m).
If a lot of devices exist within a cell as described above, an addressing method (an STID of 12 bits) used in the existing system may not accommodate a lot of devices.